In the field of the disclosure, various types of optical fibre sensors are used for Raman spectrometry and fluorescence spectrometry.
Their common characteristic is receiving external exciting light, such as a laser beam from a spectrometer, for example by means of an optical fibre, in order to route it to the sample to be analysed. The sensor then receives the light diffused by the sample to be analysed on the same fixed focal point from where the exciting light leaves the sensor, and then returns this light diffused by the sample to the spectrometer by means of a second optical fibre.
Conventionally, the sensors comprise several optical elements, such as lenses, mirrors, filters or optical fibres.
However, at the present time, sensors are of the so-called single axis type. In other words the optical elements are fixed, which implies a single fixed point situated either perpendicular or parallel to the axis of the sensor. This limits the use of the sensors according to the location of this focal point.
In fact, under certain conditions, it is desirable to be able to modify the position of the focal point. This is possible with known sensors only by modifying the position of the sensor overall (which involves relatively long adjustment times) or by having recourse to two different sensors (which of course tends to considerably increase the cost of the device).
Moreover, each spectrometer must have its own light excitation source that is integrated in it or use an external light excitation source situated close to this spectrometer.
This proves to be fairly impractical in terms of installation.
In addition, these spectrometers are generally limited to a single wavelength for the light excitation source.